Cleaning a Microwave Over the Stove

Does anyone have any idea on how to clean the vents on the front of your over the stove microwave? I am guessing it is where the fan blows through and it feels like grease or something has settled in the vents and I cannot figure out how to clean that area. Thanks.

I used to use a butter knife with a rag over it. Then, after nine years I accidentally discovered that the whole vent part can be snapped off, like the grill at the bottom of a refrigerator. See if yours can be taken off. Then you can spray it down and clean it with a brush in the bathtub. A lot easier!